The present invention relates to a laser machining apparatus for perforating or cutting using a laser beam. More particularly, this invention relates to a laser machining apparatus in which a laser beam emitted from a laser beam source is split into a plurality of beam splits different in optical path, and then the beam splits are made incident on one machining lens and condensed to machine different positions on a work concurrently.
For example, a laser beam emitted from a laser beam source is split into a plurality of beam splits different in optical path, and the beam splits are condensed by two-dimensional scanning optical systems and machining lenses prepared for the beam splits respectively, so as to machine holes in different positions of a printed circuit board mounted on an XY stage, as disclosed in Japanese Patent Laid-Open No. 58055/1999.
In this case, a region which can be scanned optically is limited. Therefore, first, the printed circuit board is positioned by the common XY stage so that a limited region is machined by optical scanning. After that, the XY stage is moved to machine the next region. Such an operation is repeated till machining is terminated.
However, this technique requires as many expensive machining lenses as the beam splits. In addition, since a region that can be scanned is limited, regions to be machined have to be allocated to be able to be perforated concurrently by the plurality of beam splits. In addition, it is difficult to allocate the regions to be machined in some machining patterns.
Therefore, in Japanese Patent Laid-Open No. 314188/1999 or Japanese Patent Laid-Open No. 2000-190087, two scanning optical systems are associated with one machining lens so that the machining speed is improved. In this case, it is not necessary to allocate regions to be machined. Thus, the workability can be improved.
However, the two optical scanning means cannot be placed in optimum positions with respect to the machining lens. Thus, there is a problem that machining beams are incident on the surface of the printed circuit board at an angle significantly shifted from the perpendicular to the surface of the printed circuit board so that the axes of the machined holes are inclined. Further, there is no reference to a method for making three or more beams incident on one machining lens so as to further improve the machining speed while reducing the price of the apparatus.